One major advantage of known mechanical governors are their simplicity and low cost of production. However, use of mechanical governors reduces the fuel system's flexibility. One problem is the relatively high fuel backup characteristic of some fuel injection systems. High fuel backup causes increased full load fuel delivery as the engine's speed is decreased from rated speed. While some fuel backup is desirable for torque rise, excessive backup causes high torque rise, smoke and exhaust emissions. Space constraints also limit governor design flexibility because of existing design envelopes. Some mechanical governor designs include means for increasing the fuel control rack travel as speed decreases. This effectively increases fuel backup in addition to the natural characteristic of the fuel injection system. This mechanism is known as a “torque capsule”, and is used to tailor the torque rise of an engine to a specified amount. However, the limitations of known “torque capsule” and governor designs is that they can only be used to increase torque rise, but not to decrease it, as is needed at some engine ratings.
Accordingly, there is a clear need in the art for an improved mechanical governor design embodying a “torque capsule” that will allow for both an increase and a decrease in torque rise depending on the needs of the engine and fit within existing design envelopes.